The MD16RP had external trigger inputs as standard.
I have one but at some point someone has disconnected all the connections from the trigger input board and i have no idea where to wire them back in. The main boards from all of the MD16 versions are the same, but unfortunately the trigger board isn't on the schematics.
You'd need the MD16RP operating system.
Alternatively a 4066 wired across the front panel buttons would probably work.